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FreeBSD-EN-21:02.extattr                                        Errata Notice
                                                          The FreeBSD Project

Topic:          UFS extattr corruption

Category:       core
Module:         UFS
Announced:      2021-01-29
Affects:        FreeBSD 11.4
Corrected:      2021-01-18 18:54:32 UTC (stable/11, 11.4-STABLE)
                2021-01-29 19:20:02 UTC (releng/11.4, 11.4-RELEASE-p7)

For general information regarding FreeBSD Errata Notices and Security
Advisories, including descriptions of the fields above, security
branches, and the following sections, please visit
<URL:https://security.FreeBSD.org/>.

I.   Background

Named extended attributes are meta-data associated with vnodes representing
files and directories.  They exist as "name=value" pairs within a set of
namespaces.  The UFS filesystem supports extended attributes.

II.  Problem Description

Under certain conditions FreeBSD 11.x releases may produce a corrupt extattr
file, and later attempts to access these extended attributes may result in
system misbehavior.  For example, lsextattr may spin at 100% CPU until the
system is shut down.

The issue that results in corrupt extattr data is not present in supported
FreeBSD 12.x versions.

III. Impact

The system may not function as required with extended attributes in use.

IV.  Workaround

No workaround is available.  Systems not using extended attributes are not
vulnerable.

V.   Solution

Upgrade your system to a supported FreeBSD stable or release / security
branch (releng) dated after the correction date, and reboot.

Perform one of the following:

1) To update your system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for an errata update"

2) To update your system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 11.4]
# fetch https://security.FreeBSD.org/patches/EN-21:02/extattr.patch
# fetch https://security.FreeBSD.org/patches/EN-21:02/extattr.patch.asc
# gpg --verify extattr.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/11/                                                        r369045
releng/11.4/                                                      r369154
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244089>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-21:02.extattr.asc>
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